Properties Of Plasma Jet Research Articles

Electrical properties determine the liquid flow direction in plasma–liquid interactions

During atmospheric pressure plasma impingement, plasma induced liquid flow will influence the transport and distribution of plasma generated charged and reactive species in liquids. We use particle image velocimetry and supplementary pH, conductivity and temperature measurements to investigate electrical properties of an AC kHz plasma jet interacting with water and electrolytes. We observe that the dominant driving mechanism in low conductive solutions are surface forces such as shear stresses and stagnation-pressure induced dimpling. These give upwards flows beneath the plasma–liquid interaction point. In highly conductive solutions, such as water with dissolved salts, the dominant driving mechanism is electro-hydrodynamic forces, with flows directed downwards underneath the plasma jet in our system. We therefore demonstrate that the direction of initial plasma induced liquid flows can be controlled through the addition of salt ions. In electrically grounded salt solutions, we also observe time resolved flow direction switching, possibly due to modification of salt solutions via electrolytic and plasma induced reactions changing the dominant flow mechanism over time.

Influence of duty cycle on the physicochemical characteristics of an AC-driven argon plasma jet and its impact on hydrogen peroxide production and cell viability

This paper investigates how the duty cycle influences the production of hydrogen peroxide (H2O2) in an alternating current (AC)-driven plasma jet. H2O2 is a major reactive oxygen species produced by plasma jets in medicine and is a biological important molecule because it can intervene in cellular signaling processes important for disease treatment. In this study, duty cycles were varied from 9% to 72%, which correlated with an increase in the plasma’s dissipated power and UV photon energy density, and consequently an increase in the production of high energy plasma components important for producing H2O2 through electron collision and UV photolysis reactions. Cell media treated with the plasma jet at higher duty cycles correlated with a decrease in the viability of HaCaT keratinocyte skin cells. The AC-driven plasma jets were shown to be operated optimally at a biocompatible gas temperature of below 40 °C whilst still maintaining efficiency in H2O2 production. Overall, the data presented in this study might find use for the future of optimization of the electrical properties of AC-driven plasma jets in plasma medicine.

Optical properties of low-pressure DC Ar plasma torch with N2–SiH4–B2H6 gas mixture injection for Si–B–N thin film deposition

Si–B–N ceramic hard films were prepared by injecting N2+SiH4+B2H6 reaction gas into an argon DC arc plasma jet at reduced pressure. XPS, FT-IR, SEM, and microhardness tester were used to characterize the samples, and the optical properties of Ar discharge plasma jet with and without reaction gas injection were studied by a multichannel high-resolution spectroscopy and a wide spectral range spectroscopy. It is found that the deposited films are mainly composed of Si, B, N and O. The film surface presents a dense structure with hundred-nanometer-sized clusters, and the hardness of sample is greatly enhanced. When the reaction gas is injected into the plasma jet, the emission of excited atoms in the background plasma is greatly reduced, and the growth rate of Si–B–N film shows a significant downward trend as the reaction gas injection ring or substrate holder is moved away from the torch nozzle. A slight enhancement of background plasma emission is observed near the substrate surface with increasing the distance between gas injection ring and torch nozzle, which indicates that the suppression effect of the reactive gas injection on the background plasma emission and the activation efficiency of the reaction gas are weakened, thereby reducing the deposition rate.

Effect of target material on electrical properties of a two-electrode dielectric barrier helium plasma jet

In this paper we present electrical characterization of a dielectric barrier discharge plasma jet operating with He (2 slm and 3 slm) as working gas and interacting with Cu, polyethylene terephthalate and distilled H2O targets. We used a plasma jet with two copper electrodes wrapped around a glass tube. One electrode was powered by a high-voltage sinusoidal signal of 30 kHz, whereas the other electrode and the target holder were grounded. We have performed detailed investigation of the voltage and current waveforms, phase differences, volt–current (V–I) characteristics, calculated impedances and power deposition. The aim was to determine the influence of different target materials and their conductivity on the plasma properties. We calculated the total harmonic distortion factor that showed that the current through grounded electrode depends on the conductivity of the target. We also calculated the power delivered to the plasma core and the plasma plume regions and observed that the change in the target conductance influenced the power in both plasma regions. The experimentally characterized electrical circuit was simulated by a model of equivalent electrical circuit corresponding to the plasma-off and plasma-on regime. Voltage controlled current source was added as model of a streamer formed in plasma-on regime.

Effect of an additional floating electrode on radio frequency cross-field atmospheric pressure plasma jet

Atmospheric pressure plasma jets with cross-field electrode configuration are a potential jet design for gases with high breakdown fields. This study focuses on the effect of an additional floating electrode on the cross-field plasma jet properties. Detailed experiments are done with the additional floating electrodes of different widths introduced below the ground electrode in a plasma jet with a cross-field electrode configuration. It is observed that in the presence of an additional floating electrode in the jet propagation path, less applied power is needed for the plasma jet to cross the nozzle and jet length increases. This threshold power, as well as the maximum jet length, depends on the electrode widths. A detailed analysis of charge dynamics in the presence of an additional floating electrode shows decrement in the net charge transferred radially to the external circuit through the ground electrode, and an increment in the net charge transferred axially. Increment in the optical emission intensity of reactive oxygen and nitrogen species, as well as the relative yield of ions like N^{+}, O^{+}, OH^{+}, NO^{+}, O^{-}, and OH^{-} in the plasma plume, that are crucial for biomedical applications suggest an improvement in the reactivity of plasma plume in the presence of additional floating electrode.

Flexible Cold Atmospheric Plasma Jet Sources

The properties of non-thermal atmospheric pressure plasma jets (APPJs) make them suitable for industrial and biomedical applications. They show many advantages when it comes to local and precise surface treatments, and there is interest in upgrading their performance for irradiation on large areas and uneven surfaces. The generation of charged species (electrons and ions) and reactive species (radicals), together with emitted UV photons, enables a rich plasma chemistry that should be uniform on arbitrary sample profiles. Lateral gradients in plasma parameters from multi-jets should, therefore, be minimized and addressed by means of plasma monitoring techniques, such as electrical diagnostics and optical emission spectroscopy analysis (OES). This article briefly reviews the main strategies adopted to build morphing APPJ arrays and ultra-flexible and long tubes to project cold plasma jets. Basic aspects, such as inter-jet interactions and nozzle shape, have also been discussed, as well as potential applications in the fields of polymer processing and plasma medicine.

Influence of Plasma Torch Power on the Plasma Jet Properties and Microstructure of Alumina Coatings

In this study, alumina coatings were formed using atmospheric plasma spraying, increasing the torch power from 29.4 to 45.1 kW. The surface morphology of the coatings was determined using scanning electron microscopy; the elemental composition was examined using energy-dispersive X-ray spectroscopy (EDS); phase composition was investigated using X-ray diffraction; and surface roughness was determined using a profilometer. The steel surface temperature was measured using a type-K thermocouple, and the plasma jet temperature, at a distance of 70 mm, using a type-B thermocouple. Alumina particle velocity was calculated by analyzing high-speed camera footage using ImageJ software. The results indicate that plasma jet temperature, speed, and in-flight particle velocity increased with plasma torch power. Furthermore, the amount of γ-Al2O3 phase in the coating increased, and the α-Al2O3 decreased with increasing plasma power. The surface roughness (Rq) of the Al2O3 coatings decreased from 7.13 to 5.54 μm, with an increase in torch power. The EDS measurements indicate that the increase in torch power did not affect the elemental composition of as-sprayed coatings. The results provide a wider understanding of an atmospheric plasma spray technique, optimizing and controlling the parameters using air as a primary gas.

On the Generation of Plasma Jets in the Kilojoule Plasma Focus Device

—Laser–optic methods were used to study the properties of plasma jets generated in the KJ Plasma Focus device. Measurements of the plasma jet velocity were conducted immediately after its appearance. During the first 10 ns, the average velocity is about 5 × 107 cm/s, which corresponds to energy of 18 keV for the ions of nitrogen, which was the working gas of the PF setup. The jet density and velocity decrease manifold over distance of 2–3 cm from its generation point. The experiments confirm that the main reason of jet generation is the necking of the pinch. It was found that after the pinch decay, a new plasma column appears, which propagates in the axial direction.

Relationships between arc plasma jet properties and plasma/liquid interaction mechanisms for the deposition of nanostructured ceramic coatings

Ceramic nanostructured coatings with intermediate thicknesses between 10 and 100 µm give improved thermal and mechanical properties when used as thermal barrier coatings or wear-resistant coatings. Such coatings comply with the technical requirements of aeronautical and automotive applications. This implies the development of deposition processes with high throughput and deposition rates to promote the formation of nanostructured coatings. The use of a liquid phase as a carrier medium for nanoparticles or solution precursors is of major interest for injection within a thermal plasma jet. The as-sprayed materials can form ceramic nanostructured coatings provided the liquid injection, encompassing the physicochemical properties of the liquid and its injection method, can withstand the plasma properties. The repeatability of the interaction phenomena between the liquid phase and the arc jet has a key role in the efficiency of deposition, and some research efforts are devoted to stabilizing the arc while the liquid jet is continuously injected within the plasma. Alternatively a pulsed arc plasma jet can be generated and is associated with a time-phased injection of droplets. This paper presents the different issues related to the arc plasma properties produced by direct plasma torches, including arc instabilities and their influence on plasma/liquid interaction mechanisms leading to the formation of nanomaterials. There is a focus on pulsed plasma spraying associated with synchronized injection of microsized droplets by means of an inkjet printing method.

Effect of flow rate of shielding gas on distribution of particles in coaxial double-tube helium atmospheric pressure plasma jet

In the application of atmospheric pressure plasma jet, the influence of ambient gas cannot be ignored, especially in some specific scenarios which are highly sensitive to ambient particles. Coaxial double-tube plasma jet device is a promising method of controlling the chemical properties of jet effluent by restraining the mutual diffusion between jet effluent and ambient gas. In this work, the discharge characteristics and chemical properties of coaxial double-tube helium atmospheric pressure plasma jet at different flow rates of shielding gas are studied numerically, and the model is validated by experimental optical images. The results illustrate the enhanced discharge at the high flow rate, the weaker discharge at the low flow rate, and discharge behaviors without shielding gas as well. With the increase of shielded gas flow rate, the particle density increases in the discharge space, which can be attributed to the wider main discharge channel caused by the increase of shielding gas flow rate. In addition, the analysis shows the great difference in ion fluxes affected by the flow rate of the SG between the contour lines of different helium mole fractions. This study further reveals that different discharge positions have a great influence on the generation of nitrogen and oxygen particles, thus deepening the understanding of influence of shielding gas flow rate on discharge behavior, and may open up new opportunities for the further application of plasma jet.

Theoretical and experimental investigation of Tialloy powder production using low-power plasma torches

This study was carried out to investigate the possibility of titanium alloy metal powder production using low-power plasma torches. An argon DC non-transferred arc plasma torch was designed, and numerical analysis was conducted to determine the plasma jet properties and wire temperature. The highest velocities inside the nozzle attachment were between 838 and 1178 m/s. The velocities of the jets at the apex were between 494 and 645 m/s for different gas flow rates. The studied plasma gas flow rates had no significant effect on the effective plasma jet length. It was shown that the plasma jet length can be estimated by numerical analysis using the temperature and velocity changes of the plasma jet over distance. It was observed that the powders produced were spherical without any satellites. As a result of this study, a plasma torch was developed and powder production was performed successfully by using relatively low torch power.

Determination of electron properties of a helium atmospheric pressure plasma jet with a grounded metallic target

AbstractAn atmospheric pressure plasma jet (APPJ) was configured to generate helium atmospheric pressure plasma. A kilohertz AC voltage was applied to APPJ electrodes, and a grounded aluminum target was placed outside of a quartz tube on the plasma propagation axis. The electron temperature and density of APPJ were determined using the emissivity of continuum radiation in 380–500 nm spectra. Electron temperatures and densities for the helium plasmas with and without a target were compared. When the target was installed, the continuum radiation was enhanced, and electron density increased. Spatial distributions of electron temperature and density from the nozzle of the quartz tube to the target were examined. The electron temperature increased up to ∼2.75 eV, and electron density increased and decreased along APPJ propagation.

Generation of non- thermal plasma jet using ZVS Driver with flyback transformer

The DBD plasma jet are generated using ZVS with flyback transformer, The equivalent circuit of ZVS driver was simulated by Multisim program, The data from simulation gave a good agreement with experimental data voltage, power and frequency . Furthermore, the electrical and optical properties of DBD plasma jet are obtained using analytical techniques, and it have been found that the system operates at voltages exceeding 9 kV, frequency 100 kHz and power of 5.67 Watts. Also, the measurement of reactive species produced in non-thermal plasmas NO and NOx with time are investigated. This jet was developed for medical applications and the effects of its emissions on microorganisms.

Properties of DBD Plasma Jets Using Powered Electrode With and Without Contact With the Plasma

An experimental investigation comparing the properties of plasma jets in dielectric barrier discharge (DBD) configurations using a powered electrode with and without a dielectric barrier, while keeping a second dielectric barrier over the grounded electrode, is reported in this work. For this purpose, two different power sources were used to produce the plasma jets, with one of them producing a pulsed high-voltage (HV) output and the other one producing a pulse-like HV output, which consists of a damped sine HV waveform. Measurements of plasma parameters were performed for both configurations using argon and helium as working gases. As a result, if the pulsed power source is used, significant differences were found in discharge power ($P_{plasma}$), rotational and vibrational temperatures ($T_r$ and $T_v$, respectively) when switching from one configuration to the other. On the other hand, using the pulse-like HV only the $P_{plasma}$ parameter presented significant differences when switching the electrode's configuration. For the pulsed source it has been observed that despite the remarkable increase in $P_{plasma}$ when changing from the double barrier configuration to the single barrier one, the values obtained for $T_r$ and $T_v$ also increased, but not in the same proportion as the increase in $P_{plasma}$, which suggests a non-linear dependency between temperatures and discharge power in the plasma jet. As an example for application of plasmas in both configurations, tests in an attempt to remove copper films deposited on alumina substrates were performed and, as a result, there was significant material removal only when the powered electrode was in contact with the plasma. As a general conclusion, if higher power is really required for some application it is better to use this configuration.

The influence of gas humidity on the discharge properties of a microwave atmospheric-pressure coaxial plasma jet

This paper investigated the influence of gas humidity (1%, 3%, 8%, 10%, and 12%) on the characteristics of a microwave-induced atmospheric plasma jet. The plasma discharge was generated by a microwave solid-state source with a H2O–Ar mixture gas flow of 8.1 L/min. The variation in energy efficiency, O and OH concentrations, rotational temperature of heavy species, shapes of plasma plumes with different humidities, and microwave input powers were recorded and analyzed. The results showed that the concentrations of O and OH increase monotonously with gas humidity at higher input powers while they fluctuate with gas humidity at lower input powers. With an increase in the H2O/Ar ratio from 1% to 12%, the energy efficiency of the plasma generator decreases, and the plasma plumes become shorter and thinner. The rotational temperature of plasma at the nozzle also showed positive correlation with increasing humidity. Adding more input power would make all the values of these parameters increase. This paper is supposed to be helpful for the research of the interaction mechanism of mix gas plasma and microwave power and for improving the effect of plasma treating biomedical materials.

The Feasibility Study of Plasma-activated Water as a Physical Therapy to Induce Apoptosis in Melanoma Cancer Cells In-vitro.

Low-temperature plasma (LTP) has demonstrated great potential in biomedicine, especially in cancer therapy in-vivo and in-vitro. Plasma activated water (PAW) as an indirect plasma therapy is a significant source of reactive oxygen and nitrogen species (RONS) which play an important role in apoptosis induction in cancer cells. In this study, Helium (He) plasma jet operating in 0.75 W and 20 kHz as dissipated power and frequency, respectively, is used as the cold plasma source. The electrical, thermal, and spectroscopic properties of (He) plasma jet and pH as well as the conductivity and temperature of PAW samples, are investigated. The concentration of hydrogen peroxide (H2O2), nitrite (NO2-) and nitrate (NO-3), which are produced in water as long-lived anticancer RONS, was measured 471.6, 7.9 and 93.5 μM, respectively after 6 min of plasma treatment. Alamar Blue and flow cytometry assays were employed to investigate the B16F10 cancer metabolic activity and apoptosis. These data support that cold atmospheric plasma (CAP) can produce a certain concentration of anti-cancer agents in water and induce apoptosis in melanoma cancer cells due to RONSs via activating the caspase 3 pathway.

Analysis of Two Calculation Methods of Heat Flux Based on Slug Calorimeter

The temperature of plasma jet is difficult to be measured directly because of its high temperature. The heat flux is often used to measure the thermodynamic properties of plasma jet and high temperature flow field. In this paper, two methods of heat flux calculation using slug calorimeter in plasma jet flow field are analyzed. One calculation method is based on one dimensional thermodynamic equation, ignoring the heat loss in the measurement process, called the noloss calculation equation; the other calculation method is to subtract the heat loss from the noloss method. This paper uses numerical simulation and experimental methods to verify the accuracy of the two heat flux calculation equations. The heat flux value is calculated according to the measured data, and the temperature curve is calculated in reverse from the calculated heat flux value. Finally, the calculated temperature curve is compared with the measured temperature curve. The temperature curve with loss heat flux is more consistent with the measured temperature curve. The loss calculation equation can obtain a more accurate heat flux value than the noloss calculation equation, and the error between the two is within 10%. The loss equation is calculated accurately, but it is difficult to give real-time results. There is an error in the noloss equation, but the calculation is simple and gives real-time results.

CHARACTERIZATION OF NEON PLASMA JETS GENERATED BY DIELECTRIC BARRIER DISCHARGE-LIKE SYSTEM AT ATMOSPHERIC PRESSURE

In this study, neon plasma jets were generated by dielectric barrier discharge-like (DBD-like) system using alternative current (AC) power supply at atmospheric pressure. The optical emission spectroscopy allowed to characterize plasma jet. The optical emission spectra were recorded to determine the properties of plasma jets with different AC voltages and neon gas flow rates. The spectra of neon plasma jets were analyzed by comparing them with the data obtained from National Institute of Standards and Technology (NIST). The results show that intensity of the spectral lines of plasma jets increases with increasing voltage applied to neon gas. In addition, neon plasma jet length was investigated for different conditions. By varying the gas flow rate of neon while the power input and frequency are kept constant, it is observed that the plasma jet length ranges from about 1.0 to 2.2 cm.

Thermal and Optical Study on the Frequency Dependence of an Atmospheric Microwave Argon Plasma Jet

This paper presents the frequency- and power-dependent thermal and spectral properties of a microwave argon plasma jet in the gigahertz range. These properties are determined at 1.3 GHz, 2.4 GHz, and 3.5 GHz for input powers from 2 W to 15 W and gas-flows from 1 to 4 Lm−1, including the influence of an argon/nitrogen mixture. These investigations are performed to determine the specific influence of the excitation frequency on the spectral properties of the plasma. The gas temperature is determined via the hydroxyl radical (OH) rotational band around 310 nm by fitting the simulated spectrum to the measurements. It is shown that high temperatures above 1350 K are generated inside the plasma for an input power of 10 W. At the same time, selective discharge 2-D mapping is realized as a result of charge-coupled device (CCD) imaging through optical bandpass filters, corresponding to the OH, N2, Ar, and H spectral emission lines. It is found that all the investigated species change their size proportional to the size of the plasma. Influence of nitrogen is investigated by generating an argon/nitrogen gas mixture. The nitrogen admixtures up to 2% are examined. These investigations are based on measurements of the N2-band around 370 nm. A strong dependence of the discharge appearance on the nitrogen content is found.

Characteristics of a radio-frequency cold atmospheric plasma jet produced with a hybrid cross-linear-field electrode configuration

Cold atmospheric plasma (CAP) jet has wide applications in various fields including advanced materials synthesis and modifications, biomedicine, environmental protection and energy saving, etc. Appropriate control on the volume, temperature and chemically reactive species concentrations of the CAP jet is of great importance in actual applications. In this paper, an radio-frequency atmospheric-pressure glow discharge (RF-APGD) plasma generator with a hybrid cross-linear-field electrode configuration is proposed. The experimental results show that, with the aid of the copper mesh located at the downstream of the traditional co-axial-type plasma generator with a cross-field electrode configuration, a linear field between the inner powered electrode of the traditional plasma generator and the copper mesh can be established. This liner-field can, to some extent, enhance the discharges at the upstream of the copper mesh, resulting in small increments (all less than 12.5%) of the species emission intensities, electron excitation temperatures and gas temperatures by keeping other parameters being unchanged. And due to the intrinsic transparent and conducting features of the grounded copper mesh to the gas flowing, electric current and heat flux of the plasma plumes, a plasma region with higher concentrations of chemically reactive species and larger plasma plume diameters is obtained at the downstream of the grounded copper mesh on the same level of the gas temperature and electron excitation temperature compared to those of the plasma free jet. In addition, the charged particle number densities at the same downstream axial location of the grounded copper mesh decrease significantly compared to those of the plasma free jet. This means that the copper mesh is also, to some extent, helpful for separating the chemically reactive neutral species from the charged particles inside a plasma environment. The preceding results indicate that the cross-linear-field electrode configuration of the plasma generator is an effective approach for tuning the characteristics of the RF-APGD plasma jet in order to obtain an appropriate combination of the plasma jet properties with higher chemically reactive species concentrations, especially relative higher number densities of neutral species, larger plasma volumes and lower gas temperatures.